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Topic: Testing/matching DPA4060's (Read 3127 times)

(I used to use Gefell UM70's or Josephon C42MP's when taping...a Rode NT4 in the early days...but I've never used these small DPA's on stands or for stealth...I'm just going through all the threads here to gather more 'real world' info on the 4060's....)

I've got a handful of DPA 4060's...some used but a good quantity of unused/unterminated ones. I've tested a bunch - no issues yet and they are fine against a known good 4060...So I soldered a pair up to Sennheiser 1/8" and bought a pair of Rode VXLR+ adaptors - to my ears they are matched very well - I've recorded sources individually through both to compare and used them in a temporary stereo setup (stereobar and tape) but I want to actually match a pair for myself to keep....and if I do that I probably should match the rest up into pairs. I might even keep a pair to place into a dummy head for binaural studio stuff...

I have access to a nice pro studio that's quiet and well treated...I have mastering grade Tannoy 8" and 10" dual concentric speakers to use as a source - I could easily build a jig to place the microphone at a specific difference so they all receive the same test conditions. I know I won't be getting a true 'frequency response' of the mic itself (I've been in a few anechoic chambers) but a frequency sweep should allow me to see which ones respond the same.

I get all the nuts and bolts of this...it's just the software....It seems Fuzzmeasure is the one I want...but i'm just not a Mac guy.

Ultimately what I would be looking to do is overlay frequency response graphs to compare mics...I see Room EQ Wizard/Spectrum Lab and ARTA for the PC...anything i'm missing?

Sorry - and a followup DPA4060 question....it says on the spec sheet they can handle 134dB SPL levels....why do most folks use 4061's then? I've seen a few mentions that 4060's aren't the right choice for loud rock stuff...

^ 4060 ultimately clip at 134dB, yet distortion rises rapidly above a level below that. The typical taper scenario where this becomes a problem is reflected in distorted bass when recording high-output PA subwoofers at high SPLs. The mics aren't clipping, but the high SPLs at low frequencies combined with the extended low frequency response of these omnis down to very low frequencies can produce audibly objectionable distortion through the entire frequency range.

This doesn't happen often, and when it does it can be hard to know if the distortion is generated in the microphone FET stage, or by the high output level of the sensitive 4060 overdriving a following amplification stage such as a preamp or the mic-input stage of a recorder.

4061 avoids the problem with a combination of less sensitivity + higher distortion and clipping thresholds. The new Core version of the 4060 may also avoid the problem by providing lower distortion overall + an increased distortion onset threshold, even though max SPL remains the same as the standard 4060.

I'm not much help with suggestions for measurement software to help with matching, but it sounds like your protocol for doing so is likely to be good. A match of relative frequency response and output level should be sufficient for that.

I use both 4060 (stealth) and 4061 (open). I'm currently in need of attempting a re-cabling of 4 of my 4060s which have failing jackets that are rapidly falling apart, or at least attempting a re-jacketing + retermination of their existing cables. I've not attempted this before so not sure how it will go. Instead, if you find you have 4 closely matched 4060, I'm interested in buying them from you to replace these. FYI, I'll re-terminate the four to a single 6-pin mini-XLR which is the input format of the 4-channel preamp I use with them.

I recall reading that the 406x frequency response is so consistently uniform, even across manufacturing batches, that good matching can be achieved by just matching on sensitivity. I can't remember where I saw it, though. Personally, I would ask Len at Core Sound for some tips, as he matches his 4060 pairs...

4060 ultimately clip at 134dB, yet distortion rises rapidly above a level below that. The typical taper scenario where this becomes a problem is reflected in distorted bass when recording high-output PA subwoofers at high SPLs. The mics aren't clipping, but the high SPLs at low frequencies combined with the extended low frequency response of these omnis down to very low frequencies can produce audibly objectionable distortion through the entire frequency range.

You can spend your entire life learning about taking and interpreting acoustic measurements. To do it well is not easy, especially “at home” even if you have a studio. That does not mean it can’t be done, just that you need to know some of how your results may deviate from those at a legit test lab.

It is difficult to separate the effects of the room (reflections) you are in, from the direct test signal hitting the capsule. This is especially bad at low freq since you need to have the signal source a fair distance away to develop enough of a wave to measure. It will quickly become apparent, that to eliminate any room reflections, and to get accurate low freq results, you need a gigantic anechoic chamber or a very tall platform outdoors above ground. Most people don’t have those. . There are other “nearfield” techniques to get around this for loudspeaker response measurements you will find.

At the other end of the spectrum you run into issues too. Even small changes in the positioning of the capsule in relationship to the sound source (tweeter is usually getting very directional itself at these frequencies too) make a difference, along with the mechanical contraption you are using to hold the capsule causing reflections at these freqs. Don’t expect to be able to easily “match” the responses here. Your measurements may not be accurate enough to make valid comparisons.

Obviously, legit mic manufacturers have developed better tools for doing this, like dedicated test mic couplers and other specialized techniques that eliminate a lot of these issues, but again, most people won’t have access to those.

Luckily for you, you are starting with great mics (DPA) and can get really good results as others have mentioned just matching the sensitivities. Their freq responses will likely be very close.

Free acoustic software for room correction like REW will work fine for what you want to do. If you look at the time response of a sweep you take, look for the first reflection’s arrival time. Anything arriving after that will be corrupted by room response and will limit your LF measurement capabilities. Gate the measurement here and ignore the response below the LF freq point this corresponds to. It will be determined by the distance between your sound source - the capsule you are measuring - and the closest reflective surface. Check out Fig 6 in this fundamental paper by Struck and Tempe. https://pdfs.semanticscholar.org/95cc/acd898f6b30fd2dbad3bbb4ba2a12ab53744.pdfThey have a much better handle on this than me.

Keep in mind, your sound source (monitor speaker) will not have a perfectly flat response and the “reference” mic you use to compare the capsules to will not be perfect either.

Taking sensitivity measurements using full bandwidth pink noise should be pretty easy. If you position the mics the same way each time, close to the front of the speaker and in line with the tweeter, you should get pretty repeatable measurements. Try positioning a capsule, taking a sensitivity measurement. Remove the mic from your test set up and then reposition it in the same spot again. Take a second measurement of the same mic. Are these two measurements the same?? Should be pretty close if you are in the same spot. This should give you some idea how varied the responses will look at HF.

There are other threads, from many years ago here, where people discussed doing these kinds of measurements and even attached some pics and graphs. Might try searching for more info here and on the web. There’s lots out there....

Sorry - and a followup DPA4060 question....it says on the spec sheet they can handle 134dB SPL levels....why do most folks use 4061's then? I've seen a few mentions that 4060's aren't the right choice for loud rock stuff...

4060's will overload many preamps with high levels, especially preamps on portable recorders with no ability to pad the signal. I have run 4060's for years at rock clubs with a Sony Minidisc recorder using the line input rather than the mic input, and levels are perfect. I have not personally noticed a low frequency distortion aspect, but I also have not used a 4061.

You can spend your entire life learning about taking and interpreting acoustic measurements.....

Cheers MIQ thanks for solid advice - clear and concise reality. I'm going to do some digging here on taperssection and elsewhere when I can as really it's just time that has kept me from tackling this properly...

I've worked for several speaker manufacturers and experienced the reality of proper anechoic chambers for measurements - I've just never measured the mics themselves. There is a proper anechoic chamber near me I can drop serious $$$ on to rent out to really do a test...but I just want to frequency match microphones to best pair them up with the plans to keep a pair and sell the rest. I've used MLSSA in the past and have some experience with SMAART and i'm pretty sure the functionality is within that software. Really, as long as i'm able to overlay frequency plots and screencap or otherwise save to a file i'm happy.

Cheers!

I know enough to look for floor bounce/first reflection and to ignore the LF in general in any space that isn't anechoic...and I would definitely build a jig to make the test very repeatable for the 12 or so mics I need to compare. The dual-concentric speaker I would use is as acoustically close to perfect for pink noise or sweeping purposes as possible

4060's will overload many preamps with high levels, especially preamps on portable recorders with no ability to pad the signal....

This makes more sense to me than the mic itself overloading. I've tested one through the Rode VXLR adaptor straight into decent studio mic pre's (Langevin AM16/Neve Kelso/Hairball Lola etc) and put it up in front of the loudest drums and guitar amps with no distortion unless the gain was too hot on the preamp.

(and EMRR I've seen you around for years on the groupdiy board...maybe even tech talk before that! )

Which dual-concentric speaker were you planning on using? Free air or in a sealed or tuned-port enclosure?

Really I can do any of the above - I have some loose 8" and 10" Tannoy drivers I could bracket and run free air but I also have some 10" and 15" Tannoy studio monitors - the 15" are 200 litre tuned port monsters but the 10's are technically tuned port (with sandwich slots instead of round ports) that are amazingly linear when critically damped with foam in both ports. Both sets are custom built enclosures and tuned crossovers.

Sorry - and a followup DPA4060 question....it says on the spec sheet they can handle 134dB SPL levels....why do most folks use 4061's then? I've seen a few mentions that 4060's aren't the right choice for loud rock stuff...

4060's will overload many preamps with high levels, especially preamps on portable recorders with no ability to pad the signal. I have run 4060's for years at rock clubs with a Sony Minidisc recorder using the line input rather than the mic input, and levels are perfect. I have not personally noticed a low frequency distortion aspect, but I also have not used a 4061.

yeah 4060>BB >line in should be just about perfect

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